HardChemistryHigh School (11–12)Organic Compounds with Functional Groups › Alcohols, Phenols and EthersNumerical
Methyl 4-oxopentanoate, CH₃COCH₂CH₂COOCH₃, has a ketone and an ester…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Methyl 4-oxopentanoate, , has a ketone and an ester. Find how many of its two functional groups are reduced by sodium borohydride in ethanol. Find how many are reduced by lithium aluminium hydride in dry ether. Then find how many are reduced by hydrogen over palladium at room temperature and one atmosphere. Then find the least mass of LiAlH needed to reduce of the compound, if the ketone takes one hydride ion and the ester takes two, and each LiAlH can supply four. Use for LiAlH.
Need a reminder? The key ideaShow
Dichromate takes 6 electrons. Ethanol to ethanal: 3 ethanol per dichromate. To ethanoic acid: 3 ethanol per 2 dichromate. products. Atom economy . NaBH reduces C=O of aldehydes and ketones. LiAlH also reduces esters and acids.
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. A ketone and an ester. of compound.
Step 1. NaBH. It reduces the ketone to a secondary alcohol and leaves the ester: 1 group.
Step 2. LiAlH. It reduces both the ketone and the ester: 2 groups.
Step 3. Hydrogen over palladium. There is no C=C in the molecule, and a ketone or an ester is not reduced under these mild conditions: 0 groups.
Step 4. The mass. Hydride ions for one molecule: . For : . Each LiAlH supplies four: . Mass: .
Check. In practice an excess is used, because the reagent also reacts with traces of water.
Answer: 1, 2 and 0 groups, and .
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